This was paid for from the flat’s annual £30,000 maintenance grant and the rest came from the Premier’s private funds. The work included the renovation of the small 1970s kitchen, which was done before the family moved in, along with the installation of a second kitchen.

Last month, the Information Commissioner, who oversees work on the Grade I listed townhouse, criticised the Cabinet Office for failing to provide enough details about the Camerons’ refurbishment.

And he ordered the couple to provide details of improvements to the bathroom and notes between them and the builders and architects.

The bathroom notes show that the Camerons ordered an extensive refit and stripped out everything, apart from a towel rail.

Among the items removed were a cast iron bath, two basins, a vanity unit, WC and cistern, and marble and timber panels. A wall was also demolished to allow for cupboard ‘modifications’.

They installed a new basin, taps, WC suite, bath and natural slate floor tiles. Although the Camerons do not reveal the cost and make of the new items, they are likely to have been top-of-the-range.

A suspended floating ceiling was fitted in the centre of the room so six low-voltage downlights could be installed.

The notes between Mrs Cameron and the architects show that she asked for the ‘removal of existing fixtures and furnishing’ from the flat. Her specifications included the removal of ‘all existing curtains, curtain poles and curtain fittings and store if in good condition – eg sitting room damask curtains, dining room floral curtains, family room floral curtains’.

Modern style: David Cameron in the kitchen of a former home during 2006

Only four designer Howard sofas made the grade and were allowed to remain. As the notes explain, the only items that Mrs Cameron wanted to keep were: ‘2 x olive green chenille Howard sofas in 3rd floor bedroom, 1 x brown Howard armchair in child bedroom and 1 x stripey Howard armchair in child bedroom 3.’

A No 10 source said the Camerons would have used their own fixtures and fittings as replacements. Until now, the Cabinet Office, which is in charge of the upkeep of Downing Street as well as FoI requests, has refused to disclose additional details.

It claimed they were not covered by the Freedom of Information Act because they were stored by the Cabinet Office ‘only on behalf of the family of the Prime Minister’. But Mr Graham has over-ruled this.

The scale of the refurbishment could fuel accusations that the Prime Minister is out of touch with millions of families struggling to cope with soaring living costs and pay freezes.

A No 10 source said the Camerons were ‘relaxed’ about giving details of the refurbishment, adding: ‘It should be borne in mind that Downing Street is a Grade I listed building. The improved facilities will remain in the Downing Street flat when they are gone and can be used by others.’